A diverse range of formulations useful in personal care and pharmaceutical applications utilize inorganic pigments and other micronized inorganic oxides, such as physical sunscreen ingredients. Typically, these finely divided particulate products are dispersed within formulations by mixing, using either low-shear or high-shear methods. In order to make stable, cosmetically acceptable products, uniform dispersions must be produced, with all particles wetted out and which remain in suspension over a period of time without settling, jelling or agglomerating. Producing such stable suspensions has proved to be a challenge, although some successes have been achieved.
For example, U.S. Pat. No. 5,116,604 to Fogel describes the use of neopentanoate esters, in particular isoarchidyl neopentanoate, as cosmetic emollients for sunscreen products. U.S. Pat. No. 5,716,602 to Uick describes sunscreens formulated to include a water resistance agent and an insect repellent. One formulation has in it an aqueous emulsion DEET, a sunscreen agent, an anionic surfactant, an alkylated PVP, and octyldodecyl neopentanoate. Both Fogel and Uick use Octyldodecyl Neopentanoate.
U.S. Pat. No. 5,476,643 to Fogel describes the use of two specific neopentyl glycol diesters, as wetting, dispersing, spreading and detergent agents for micronized TiO2,ZnO and other pigments. These esters, neopentyl glycol di-2-ethyl hexanoate and neopentyl glycol di-isostearate, are used in varying combinations and may also be used with an emulsifying agent for a water dispersible pigmented make-up cleaner composition.
Emollients such as C12–C15 Alkyl Benzoate (Finsolv TN, Finetex, Inc.) and Tridecyl Neopentanoate (TRIVENT NP-13) have also been employed with some success as dispersants for physical sunscreens, as have various glycols and propoxylates, such as PPG-3 Myristyl Ether. See for example, U.S. Pat. No. 5,928,631 to Lucas which describes a skin composition for controlling environmental malodors on the body. The composition comprises from about 0.1% to about 5%, by weight of a solubilized, water-soluble, uncomplexed cyclodextrin; from about 0.1% to about 36%, by weight of an oil phase selected from the group consisting of emollients, moisturizers, and skin protectants; one or more surfactants, and an aqueous carrier.
Several other possibly relevant US Patents are:
U.S. Pat. No. 4,830,768 to Reich, et al. discloses a fatty propoxylated ester of dicarboxylic acid and fatty alcohol with 1–15 units of propoxylation. Lubricating properties are claimed for non-topical preparations.
U.S. Pat. No. 5,693,316 to Pereira, et al. discloses a fatty alkoxylated ester of dicarboxylic acid and a stoichiometric excess of 1 or more polyalkoxylated fatty alcohols with emollient properties for topical preparations. The preparations include mineral oil as a second emollient.
U.S. Pat. No. 5,302,377 to Periera, et al. discloses a fatty alkoxylated ester of tricarboxylic acid and a stoichiometric excess of 1 or more polyalkoxylated fatty alcohols with emollient properties for topical preparations. The preparations include mineral oil as a second emollient.
U.S. Pat. No. 5,455,025 to Pereira, et al. discloses fatty alkoxylated esters of tricarboxylic acid with a stoichiometric excess of 1 or more polyalkoxylated fatty alcohols having emollient properties for topical preparations.
U.S. Pat. No. 5,597,555 to Pereira, et al. discloses a fatty alkoxylated ester of dicarboxylic acid with a stoichiometric excess of 1 or more polyalkoxylated fatty alcohols with emollient properties for topical preparations.
U.S. Pat. No. 6,476,254 to Pereira, et al. discloses a fatty alkoxylated ester of dicarboxylic acid and fatty alcohol with pigment wetting/dispersant/emollient properties for topical preparations.
None of these references disclose mixed fatty acid esters of dicarboxylic acid and their use as effective pigment dispersants.
Thus there remains a need for superior dispersants with desirable esthetic properties for use in pigmented cosmetic compositions, particularly sunscreen formulations that contain physical sunscreens.
Additionally, since formulators often find it useful to fully disperse pigments, e.g., micronized metallic oxides, in a portion of the oil phase by high shear techniques such as milling, there is a need for forming oil phase dispersions which have a high solids content of pigments, particularly micronized metallic oxides, that are fluid.